1. Field of the Invention
The present invention relates to a motor control method for a Motor Driven Power Steering (MDPS) system, particularly a technology that allows steering operation as smooth as possible while preventing damage to a motor due to heat.
2. Description of Related Art
Unlike a hydraulic power steering system using driving force of an engine, an MDPS system provides steering force from driving force of a motor, such that it has an advantage of reducing fuel consumption of a vehicle, but is expensive as compared with the hydraulic power steering system.
Therefore, an MDPS system using an inexpensive DC motor, not a BLAC motor, has been developed to reduce the cost of the MDPS system, however, the motor has a problem in that large amount of heat is generated and it is difficult to discharge the heat.
An MDPS system is basically provided with an Over Heat Protection (OHP) logic to prevent a motor from overheating, and the OHP logic is activated earlier when using a DC motor as described above than when using a BLAC motor.
The OHP logic is provided to restrain electric current that is supplied to the motor, such that when the OHP logic is activated, the steering force supplied from the motor is rapidly decreased and a driver feels the steering wheel heavy.
Therefore, it is the main performance of the MDPS system how long it is possible to steer a vehicle before the OHP logic is activated, which is called ‘OHP performance’ and is estimated by the number of left-right full turn of the steering wheel before the OHP logic is activated under predetermined conditions.
In order to improve the OHP performance, the method of increasing the capacity of the motor have been known in the art; however, this method are not preferable because the size and capacity of the motor, such that it is difficult to mount and dispose them in a vehicle and the cost is increased.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.